The torsion blance experiment was created around 1783 by a geologist named John Michell, he also created the torsion balance apparatus for this experiment but died before the experiment was completed.
The scientist Henry Cavendish then recreated created the torsion balance apparatus in 1798 following Michell's design closely.
He did this to confirm experimentally that Newton's law of gravitation was true.
When he was asked why he was measuring the gravitational constant he said he was "weighing the Earth"
it came to be known also as the Cavendish experiment
The device did not become widely known untill Charles-Augustin de Coulomb reinvented it and used it to measure electric force.
Coulomb discovered that the electric force between objects is inversely proportional to the distance between the objects.
The Use Of a Torsion Balance
The purpose of a torsion balance is to measure very small forces, like the miniscule gravitational attraction between two small items, or small electrostatic forces.
Coulomb used the Torsion Balance experiment to create the formula which is discussed in more detail at the page Coulombs Law.
How Torsion Balances Work
A basic torsion balance is a horizontal bar suspended from a wire in a glass case. Touching the bar to begin with is a stationary vertical bar that is both on the inside and outside of the glass case.
Touching a charged object to the vertical bar will cause both bars to have the same charge causing them to seperate.
The amount of seperation that occurs can be used to determine the gravitational force or elctrostatic force exerted between the two bars.
The greater the magnitude of gravitational force or charge of the bars, the greater the fibre twists and the greater the angle of rotation is.
Why Torsion Balances Work
What causes a torsion balance to seperate is the conduction that occurs between the charged object and the vertical bar which gives the vertical bar a charge which then in turn causes the horizontal bar to get the same charge making them seperate. Then Induction keeps them seperated.
Who Created the Torsion Balance and Why?
Henry Cavendish (1731-1810)
The Use Of a Torsion Balance
How Torsion Balances Work
Why Torsion Balances Work
References